1. Field of the Invention
The present invention relates to a silicon carbide semiconductor device and a method for manufacturing the silicon carbide semiconductor device, more particularly, a silicon carbide semiconductor device having an element region provided with a semiconductor element and a termination region surrounding the element region when viewed in a plan view, as well as a method for manufacturing such a silicon carbide semiconductor device.
2. Description of the Background Art
According to Japanese Patent Laying-Open No. 2010-147222 (Patent Literature 1), a SiC semiconductor device has a cell region provided with a MOSFET and an outer circumferential region surrounding the cell region. In the outer circumferential region, a mesa structure portion constructed by a recess is formed. At a boundary portion between the cell region and the outer circumferential region, a p type resurf layer is formed to surround the outer circumference of the cell region so as to extend from a side wall surface of a stepped portion of the mesa structure portion to a bottom surface thereof. Also, a plurality of p type guard ring layers are formed to surround the circumference of the p type resurf layer. Further, an n+ type layer and a same-potential ring electrode electrically connected to the n+ type layer are formed to surround the circumferences of the p type resurf layer and the p type guard ring layers, thereby forming an outer circumference breakdown voltage structure. Moreover, a source electrode and a drain electrode are provided respectively on the front-side surface side and the backside surface side of the substrate.
In the outer circumferential region (termination region), an insulating film is normally formed on the substrate (silicon carbide substrate) for the purpose of passivation. Hence, in the outer circumferential region, an interface is formed between the substrate (silicon carbide substrate) and the insulating film. As a current is more likely to flow along this interface, leakage current is more likely to flow between the source electrode and the drain electrode (first and second electrodes). As a result of inspection by the present inventors, it has been found that when a crystallographical plane orientation of the silicon carbide substrate is inappropriate in the termination region, interface state density becomes high in the interface between the silicon carbide substrate and the insulating film, with the result that leakage current is likely to flow between the first and second electrodes.